A rotating photosensitive drum in a laser printer is exposed to a light beam from a laser source to create an image that is coated with toner and then transferred to a piece of paper. The light beam scans across the drum one line a time. However, the laser source itself does not physically move. Instead, the light beam is aimed at a movable reflective surface that simultaneously reflects and scans the light beam across the drum.
Conventional laser printers use a rotating polygonal block having multiple reflective surfaces to achieve the scanning motion. Recent innovations propose using just a single mirror with a single reflective surface, such as a Micro Electro Mechanical Systems (MEMS) mirror that oscillates about an axis.